This invention relates to a motor driven fuel pump and control system for internal combustion engines, and particularly to an apparatus and method which continuously monitors the fuel system pressure and regulates the fuel flow to a predetermined pressure, and controls the flow of fuel at an essentially constant pressure from a remote fuel tank to the engine.
Fuel delivery systems for modern internal combustion engines, particularly engines using fuel injection, generally use a motor driven fuel pump. A fuel pump operated at an appropriate manner provides for a more precise flow of fuel for injection into the engine. The fuel pump may be mounted external to or within the fuel tank. The connection may use either a single line direct flow or a constant flow with excess fuel redirected to the fuel tank via a return line. For various reasons, direct line connection without a need for the return line, is desirable.
Various prior art patents disclose the various fuel systems. For example, U.S. Pat. No. 4,756,291, which issued Jul. 12, 1988 to Cummins et al and is assigned to the Ford Motor Company, discloses a control system for a motor driven fuel pump in which a control system is provided having a high voltage limit and low voltage limit related to the flow pressure. If the flow related voltage signal rises above the high voltage limit or below the low voltage limit, the control system adjusts the motor drive, using a pulse width modulated signal. U.S. Pat. No. 5,055,758 which issued Oct. 8, 1991 to Hock is assigned to Jabil Circuit Company, discloses a motor driven fuel pump establishing an alternating current signal in combination with a voltage control signal related to the flow, which is superimposed on the alternating signal. An output drive signal is a pulse, the width of which is set by the intersecting of alternating current signal by the flow related voltage control signal. This again provides a pulse width modulated signal, which is varied each half cycle of the main supply signal.
The more recent patent to Hock '758 discloses the motor pump unit mounted within the fuel tank proper, while the earlier Cummins et al '291 patent discloses the motor and pump mounted external to the fuel tank. Generally, each prior art system can use a motor driven pump in it mounted within or external to the fuel tank, Other patents of general interest are, of course, disclosed in the above two patents.
The fuel delivery systems are required to provide fuel in relatively precise amounts to the engine and in appropriate time relation. Maintaining of a proper flow and pressure has presented various problems with respect to providing a cost effective supply system. Sensing units must be able to accurately determine the pressure characteristic. The system must be of a relatively small and compact construction while able to handle the power to drive the pump motor and a control system, and the system must have a long operating life preferably corresponding substantially to the life of an engine. Although a life of 50,000 miles of operation is generally considered a good life, a more satisfactory anticipated need is between 100,000 and 200,000 miles. The power consumption should be minimal while the motor operates under sufficient power and torque to maintain the desired flow under pressure over the total engine speed range. A smooth flow at a relatively constant pressure from the fuel tank to the engine is desirable to maintain an efficient system, with minimal fuel consumption. Further, the system must operate in the various environments encountered by engines, such as in automobiles, and preferably over the life of the engine.
The requirements for an improved fuel delivery system having the optimal characteristics thus present various considerations and demands with respect to cost, life and size. There is a present need for a compact, cost effective fuel pump unit, which can supply fuel at an essentially constant pressure at the engine without requiring significant maintenance and/or replacement during the normal life of the vehicle marine and other internal combustion engines.